Enormous progress in ocean acidification research

New report summarises current state of knowledge
Never before have so many scientists conducted research on what impacts the declining pH value of seawater has on animals and plants in the ocean. The experts have now compiled their results for the second report on ocean acidification of the Convention on Biological Diversity (CBD), which will be made public today at the twelfth conference of the Parties to the Convention. Major focus is placed on the consequences that also have an effect on us human beings. By means of this summary, the CBD wants to put the problem of the acidifying oceans on the international political agenda. The authors of the new report include scientists of the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI).

The past five years were certainly of major importance for ocean acidification research, says Dr. Felix Mark, an AWI biologist and one of the authors of the current CBD report on ocean acidification. Since 2009 when the first CBD report on ocean acidification appeared experts from all over the world have published more than 1,000 new studies on the impacts of the declining pH value of seawater on animals and plants in the ocean.

One of their major findings is definitely that acidic water not only harms the calcareous shells and skeletons of mussels and corals, but may also affect more highly developed ocean dwellers like fish. Moreover, every species reacts to acidic water very differently and some even profit from it, such as seagrasses, which utilise the additional carbon dioxide for photosynthesis.

On the basis of this new knowledge, the focus of research in recent years has broadened more and more and thus our understanding of how far-reaching the consequences of acidifying seas are as well: We are beginning to understand how individual species interact under the influence of ocean acidification, what the consequences are when a species disappears from the food web and whether animals can adapt over several generations, says Dr. Felix Mark.

Another important aspect was the approach of not viewing ocean acidification as a single phenomenon that alters living conditions in the oceans all alone. The declining pH value joins other environmental factors, such as the increasing water temperature, decreasing oxygen concentration as well as pollution and overfertilisation of the oceans. Researchers take this into consideration in laboratory and field tests in which they, for example, heat up the water in aquariums and add carbon dioxide at the same time.

AWI scientists have made a significant contribution in this context. The team headed by Dr. Felix Mark is conducting research on how ocean acidification and warming impact fish in the polar regions. For instance, we have found out that the polar cod, which is a key species for the Arctic ecosystem, reacts sensitively when the Arctic Ocean becomes more acidic and at the same time warmer. The fish then presumably does not grow as well, explains the biologist.

As AWI scientist and co-author Dr. Barbara Niehoff discovered, one of the most important food species of the polar cod, the so-called copepod, is less sensitive to such changes. Even at extremely high carbon dioxide concentrations, far above the present-day level, these creatures display no significant reactions, states the biologist.

Scientists from twelve countries have now summarised this abundance of new results for the new CBD report on ocean acidification. However, ocean dwellers that do not react at all, react only to a very minimal extent or even positively to ocean acidification play only a minor role here. As was the case five years ago, the report is primarily devoted to species that find it difficult to adapt to the more acidic water particularly corals.

As coral reefs not only number among the most species-rich ecosystems, but also supply over 400 million people with food and protect them against storm surges, they are among the most intensively investigated habitats in ocean acidification research and certainly among the most interesting, both political and economically. After all, scientists estimate that the impact of ocean acidification on corals and molluscs alone could lead to consequential costs of a billion US dollars.

In spite of the enormous leap in knowledge compared to the previous CBD report, important questions remain open, however. For example, whether sensitive dwellers like corals can still adapt fast enough to the new living conditions. Or how the ocean ecosystem as a whole reacts to acidification.

At the moment we are in the process of processing the individual available results in such a way that they can be used in ecosystem models, explains Dr. Felix Mark. In this manner the scientists hope to be able to forecast more accurately what life in the ocean could be like in the future, how food webs shift and what species might vanish forever.

In line with the objective of the convention, the current CBD report is intended to make ocean acidification and its impacts part of the international policy agenda to a greater degree. However, here, too, a lot has happened in the last five years: for instance, the IPCC has treated the problem of increasingly acidic oceans for the first time on a comprehensive scale in its Fifth Assessment Report. A step in the right direction, believes biologist Dr. Felix Mark: That certainly contributed to recognition of ocean acidification as a fact in the political arena, in particular as a fact that is for the most part caused by us humans.

Notes for Editors: The CBD report "CBD Technical Series 75: An Updated Synthesis of the Impacts of Ocean Acidification on Marine Biodiversity" is available on http://www.cbd.int/ts/.

We have compiled the following background material on the publication of the current CBD report for you:

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